1. Field of the Invention
The present invention relates to an engine comprising a variable valve timing device that varies phases of a camshaft to vary timing of opening and closing of an intake valve, an exhaust valve, or both.
2. Description of the Related Art
Some engines today include a variable valve timing device that varies the timing for opening and closing intake and exhaust valves in the engine according to the rotating speed of the engine and a load thereon. In most engines, the valves are driven off of the crankshaft in a timed relationship. A crank-side drive member is mounted on a crankshaft and a camshaft drive member is mounted on a camshaft. A timing chain or a timing belt connects these drive members together such that the camshaft(s) rotate together with the crankshaft. The variable valve timing device changes the phase of the camshaft drive member and the camshaft relative to the crank-side drive member using hydraulic pressure. Japanese Patent Publication No. JP-A-07-293210 discloses an example of a variably valve timing device that uses hydraulic pressure to change the phase of the camshaft and the camshaft drive member.
An engine provided with the hydraulic pressure-type variable valve timing device described above needs a hydraulic pressure switchover valve that switches hydraulic pressure to an advance-side or a lag-side of a hydraulic pressure chamber of the variable valve timing device. That is, the switchover valve is used to supply pressurized hydraulic fluid to either the advance-side or lag-side of the hydraulic pressure chamber of the variable valve timing device. Consequently, the variable valve timing device either advances or retards the position of the camshaft relative to the crank-side drive member. The switchover valve typically has an elongated body. In some prior applications, the size of the engine must be enlarged to accommodate the switchover valve within the cylinder head of the engine.